Ask SAIL: as the Log Turns

Q I’m trying to figure out why the paddle-wheel transducer for my Raymarine ST60 knot log is registering incorrectly. The plug is clean, and the wheel turns freely. Yesterday my speed over the ground on the GPS was 5 to 7 knots, and the speed registered 0 to 0.8. It does this periodically to irritate me, and I’d like to make it stop. Chuck E. Weiss, Los Angeles, California

DON CASEY

A. Generally when a log under-registers or shows zero, the problem is with the transducer or its cable. Paddle-wheel transducers are notorious for fouling almost instantaneously. If it works fine sometimes, fouling is likely the problem.

To test the transducer, pull it from its through-hull housing and watch the display as you spin the paddle wheel. It should spin easily and smoothly. Push the axle pin out with a stiff wire to release the paddle wheel, noting which way the paddles face. Polish the axle free of all growth with a Scotchbrite pad. You should also clean the sides of the wheel, as a small bit of debris here can cause the wheel to jam. Finally, give the transducer body and the wheel a thin coat of transducer antifouling paint. I’ve never found this to be very effective, but it does no harm.

If you still have accuracy problems, try resetting the unit to its factory settings. Your manual will show you how to do this. You will have to recalibrate the unit afterward, but resetting can clear up any electronic glitches. If the unit continues to show zero or some ridiculously low value, the transducer may be defective. Turn off the unit and disconnect the screen and the conductor wires from the head. Measure continuity between the two conductors with a multimeter while you turn the paddle wheel. A good transducer will show the circuit opening and closing with each quarter turn of the wheel.

Related

After years of quiescence in the wake of the Great Recession, iconic Island Packet is back with its new 349, a re-boot of the old Estero that not only looks great, but takes the Island Packet style of sailing performance to a new level. Design & Construction First among the many ...read more

At this past fall’s Annapolis Boat Show, SAIL magazine had a chance to corner Neel Trimarans founder Eric Bruneel and have him give us a tour of the accommodations aboard the new Neel 51, winner of the “Multihull over 50ft” category in the 2019 Best Boats contest. For a complete ...read more

The United States Coast Guard requires that all boats operating in coastal waters or on the high seas carry a selection of visual distress signals. Almost invariably, such signals include the pyrotechnic type, either handheld or fired from a flare pistol, but surely there are ...read more

It seems that we all struggle to make our start in life, searching for something that we would enjoy doing, something that not only challenges us today but will stay that way year after year, all the time giving great rewards along the way. Most things we are introduced to early ...read more

Stay Hooked Chain hooks on anchor snubber lines tend to fall off when you least want them to. Not so this latest example from Mantus. The M2 Chain Hook is secured to the chain by a simple elastic strap, so it won’t come off when the snubber loosens. Made from corrosion-resistant ...read more

When I boarded Fountaine Pajot’s new flagship, the Alegria 67, at the Cannes boat show last September, the first thing I noticed was that several groups of people were carrying on private conversations in separate lounging and seating areas in the saloon—that’s how big this boat ...read more

“Ready to take the dink ashore?” Never had those words invoked as much anxiety as when my husband, Jeff, and I first moved to the Pacific Coast. Why? Because we had exactly zero experience with dinghy surf landings, and the possibility of being flipped upside down along with our ...read more